The invention is concerned with saving thermal energy, especially thermal energy that is expended to heat water which is used for a variety of reasons in commercial establishments, such as fast food chain restaurants which generally operate on a high volume/low cost basis and are, therefore, appreciative of any savings in utilities, the cost of which has risen dramatically in the last few years.
A great deal of thermal energy is required to operate the various pieces of cooking and heating equipment that are used in such restaurants. Also, many of these restaurants employ from four to eight conventional refrigeration systems which waste tremendous amounts of heating energy to the ambient atmosphere.
U.S. Pat. Nos. 4,041,726 and 4,179,902 are directed to the use of water cooled condensers through which superheated refrigerant, from the compressors of a refrigeration system, is circulated to heat water, prior to circulation of the water to a hot water tank for storage. The '902 patent, in particular, shows and describes the use of a plate-type heat exchanger that has a waffle-like configuration through which superheated refrigerant vapor is circulated.
Such plate-type heat exchangers are known to be used in conjunction with conventional water heaters as a means of supplementing heating of the water inside the storage tank of the water heater. One, or a number of such heat exchangers, are wrapped around the outer peripheral surface of the storage tank which is usually made of steel. The waffled, plate heat exchanger is made of stainless steel to prevent any electrolytic reaction from taking place. It can be appreciated that the waffled shape of the heat exchanger consists of alternate peaks and valleys and that, at most, only the peaks will be in contact with the storage tank. Thus, the most efficient transferance of heat by conduction from the heat exchanger to the water tank, occurs only at these peak areas. Heat will be transferred between the valleys of the heat exchanger by radiation or convection which is not as efficient, since air, trapped in the valleys, acts as a thermal barrier or insulator. Stainless steel, from which such plate exchangers are made, has about ten times less thermal conductivity than copper. It can be appreciated from the above, that the above-described heat exchanger and method of adapting it to a hot water heater, are not the most desirable combination.
Moreover, the problems encountered by using such heat exchangers in connection with a number of refrigeration systems, are staggering. For example, suppose one wants to capture and use the normally wasted heating energy from six separate refrigeration systems which employ six different refrigerants that must be kept separated as they flow through the waffled plate heat exchanger. Peaks and valleys of the heat exchanger must be strategically blocked to form six, separated conduits through which the six different refrigerants are directed. Such a process is time cosuming and costly. Moreover, suppose two more refrigeration systems with two new and different refrigerants are desired to be adapted to the hot water heater. It is easily imagined that it is next to impossible to adapt the heat exchanger to accommodate two more conduits, especially if the flow of the other six refrigerants through the heat exchanger has been optimized.
The invention is designed to overcome these problems by the provision of a simple, highly efficient heat transferring device which readily adapts a conventional water storage tank for use with a number of refrigeration systems as a heat exchanger to capture and utilize in the heating of water in the tank, heating energy which is normally wasted into the ambient atmosphere from the refrigeration systems.
Briefly stated, the invention is in an energy savings and efficient water heating device and system which comprise a steel tank in which liquid is stored and heated, and a plurality of separate groups of copper coils which are formed of hollow copper tubing that has a rectangular cross-section and which is tightly coiled around the outer peripheral surface of the storage tank. A nonelectrolytic, thermal conductive bonding cement is layered between the copper coils and the steel tank to prevent any electrolytic reaction between the dissimilar metals of the coils and tank, and to fill any voids between the coils and tank to enhance the transfer of heat, by conduction, from the coils to the tank for subsequent transfer of heat to the water in the tank.
The number of groups or sets of copper coils can be easily changed to accommodate the addition or subtraction of one or more refrigeration systems. Moreover, the use of copper tubing with a rectangular cross-section produces optimum heat transferance to the storage tank. Thus, the invention has two major advantages; namely, improved heat transferance and adaptability to change.